Subleties can make all the difference.  The 21 featured an old MBL restoration and a loose contact verging on diastema and exaggerated incisal embrasure.  We adopted the pre-crimped Mylar matrix technique employed in Skulpting Skool 102 and freehanded the linguoproximal aspects of 21 and used the pull-through technique to make the contact area more uniform and simultaneously correct the midline cant.  A simple bilaminar technique was used using Kerr Harmonize Enamel A1 and Dentin A2 as pre-selected before dehydration.